北京地区一种菘蓝白粉病病原菌的鉴定

目的 明确北京地区菘蓝白粉病病原菌的种类及分类地位。方法 通过田间调查了解病害发生情况及为害特征；通过显微镜观察病原菌菌丝形态、产孢结构、分生孢子及其着生方式等；采用特异性引物ITS1/PM6扩增病原菌核糖体脱氧核糖核苷酸-内部转录间隔区，病原菌扩增序列及其高度同源序列用MegaX软件中的邻接法构建系统发育进化树。结果 菘蓝白粉病病原菌菌丝直或略弯，上有浅裂叶状附着胞；分生孢子梗直立或微弯，不分枝；顶端串生分生孢子，长椭圆形或近圆柱形；芽管在分生孢子近端处萌发，直或弯曲，芽管顶端有吸器。根据显微形态特征初步推测，该病原菌属于白粉菌目（Erysiphales）白粉菌科（Erysiphaceae）白粉菌属（Erysiphe）。核酸序列比对结果表明，其与十字花科白粉菌Erysiphe cruciferarum核酸序列（MT309701、MK341128、MF192845、KY660929）一致性均为100%。该病菌与十字花科白粉菌聚为一枝，与其他白粉菌亲缘关系较远。结论 综合形态学特征及分子鉴定结果，该菘蓝白粉病病原菌为十字花科白粉菌。

Identification of A Pathogen Causing Powdery Mildew of Isatis indigotica in Beijing

Objective To clarify the species and taxonomic status of pathogens causing powdery mildew on Isatis indigotica in Beijing.Methods The occurrence and damage characteristics of this disease were investigated in the field. Mycelium morphology, sporulation structure, conidia, and the attachment mode of the pathogen were observed by microscope. The pathogen ribosomal deoxyribonucleotide (rDNA)-internal transcribed spacer (ITS) was amplified with specific primers ITS1/PM6. The amplified sequence and its highly homologous sequence of the pathogen were used to construct the phylogenetic tree using the neighbor-joining (NJ) method in MegaX software.Results Hypha of the pathogen causing powdery mildew on I. indigotica was straight or slightly curved, with shallow lobed appressoria on it. Conidiophore was erected or slightly curved with no branches, and conidia were twinning at the top in long oval or nearly cylindrical shapes. Germ tubes germinated at the proximal end of conidia, straight or curved, with a haustorium at the top. Based on the morphological characteristics, the pathogen was preliminary speculated to belong to the genus of Erysiphe, the family of Erysiphaceae, and the order of Erysiphales. The result of nucleic acid sequence alignment showed that the pathogen had 100% nucleic acid sequence identity with those (MT309701, MK341128, MF192845, and KY660929) of E. cruciferarum belonging to the family of Brassicaceae. The pathogen was clustering with E. cruciferarum in a branch and showed a relatively far phylogenetic relationship with others.Conclusion Based on the morphological characteristics and nucleic acid sequence alignment results, the pathogen causing powdery mildew on I. indigotica was identified as E. cruciferarum.